This invention relates to a process for modifying a property of glass or vitrocrystalline material.
The term "vitrocrystalline material" denotes a material formed from glass by a treatment which produces one or more crystalline phases therein while also retaining at least one vitreous phase therein. For simplicity of expression, reference will be made hereinafter principally to glass as the material treated, although several specific examples of the treatment of vitrocrystalline materials will be given.
It is known that ions of various substances can be caused to enter the surface of a glass body from a contacting medium. By this means, various modifications can be achieved, depending on the nature of the substance which enters the glass and the conditions existing in the process. By way of example, the diffusion may bring about a change in the color of the glass or an increase in its tensile strength.
One problem which has been encountered in the performance of such a process is that of achieving a uniform modification of the glass body over the whole of its treated surface. It has been found to be difficult to solve this problem when following the usual practice of immersing the body to be treated in a bath of the treatment medium.
Another proposed treatment procedure involves discharging the liquid treatment medium onto the body to be treated so that the medium continuously streams along the body. This method appears to give better results from the standpoint of uniformity, but the pumping equipment required for recirculating the treatment medium is subject to corrosion by such medium.